References considered to be relevant as background to the presently disclosed subject matter are listed below:                H. Pham, H. Ding, N. Sobh, M. Do, S. Patel, and G. Popescu, “Off-axis quantitative phase imaging processing using CUDA: toward real-time applications,” Biomed. Opt. Express 2(7), 1781-1793 (2011).        P. Girshovitz and N. T. Shaked, “Real-time quantitative phase reconstruction in off-axis digital holography using multiplexing,” Opt. Lett. 39(8), 2262-2265 (2014).        S. K. Debnath and Y. K. Park, “Real-time quantitative phase imaging with a spatial phase-shifting algorithm,” Opt. Lett. 36(23), 4677-4679 (2011).        B. Bhaduri and G. Popescu, “Derivative method for phase retrieval in off-axis quantitative phase imaging,” Opt. Lett. 37(11), 1868-1870 (2012).        Y. Xu, Y. Wang, W. Jin, C. Lv, and H. Wu, “A new method of phase derivative extracting for off-axis quantitative phase imaging,” Opt. Communications 305, 13-16 (2013).        B. Sha, X. Liu, X. L. Ge and C. S. Guo, “Fast reconstruction of off-axis digital holograms based on digital spatial multiplexing,” Opt. Express 22(19), 23066-23072 (2014).        M. A. Herráez, D. R. Burton, M. J. Lalor, and M. A. Gdeisat, “Fast two-dimensional phase-unwrapping algorithm based on sorting by reliability following a noncontinuous path,” App. Opt. 41(35), 7437-7444 (2002).        
Acknowledgement of the above references herein is not to be inferred as meaning that these are in any way relevant to the patentability of the presently disclosed subject matter.